The Pathology and Veterinary Service Core is centered at Harvard Medical School's New England Primate Research Center (NEPRC). The objective of this core is to provide highly integrated clinical management and pathology expertise to project leaders and individual investigators. The Pathology and Veterinary Service Core will house and care for the macaques used in this program project. The core will be responsible for the daily clinical care of animals and all animal procedures such as inoculating the animals with virus, blood draws, health exams and intestinal and lymph node biopsies. Titration of viral stocks for intravenous and mucosal challenge experiments will be conducted through the core. The laboratory component of the core will also perform hematology, clinical chemistries, microbiology, and serology for SIV and other potential pathogens. Pathology services will include necropsy and diagnostic procedures as well as specialized techniques in support of specific research aims such as immunohistochemistry, in situ hybridization, quantitative image analysis and laser confocal microscopy. Many of the laboratory and pathology procedures were first developed by investigators at the NEPRC, are well established and have been published on extensively. Individuals responsible for these varied tasks are members of the NEPRC faculty and staff who have previously worked closely on numerous projects. This integrated and multidisciplinary approach has been critical to the success of other multi-project grants within the AIDS research program at NEPRC. The specific aims of this core are: Specific aim 1: To provide well defined research animals through centrally managed cohorts in of support program project research objectives. Specific aim 2: To provide comprehensive animal husbandry and clinical services in the implementation of research project objectives. Specific aim 3: To provide pathology core services in support of program project objectives.